1. Technical Field of the Invention
The present invention relates generally to a power conversion apparatus equipped with electronic components such as semiconductor modules, and more particularly to such a power conversion apparatus equipped with a grommet inserted into a wall of a casing to establish a hermetic seal.
2. Background Art
Usually, electric vehicles or hybrid vehicles are equipped with a power conversion apparatus such as an inverter or a DC-DC converter.
The power conversion apparatus is known which is equipped with electronic components such as semiconductor modules which make up a power converter circuit, a cooler which works to cool the electronic components, and a casing in which the electronic components and the cooler are disposed.
The cooler includes a coolant inlet pipe and a coolant outlet pipe. The casing has formed therein cut-out portions through which the coolant inlet pipe and the coolant outlet pipe pass. Elastic grommets are fit in the cut-out portions to hermetically seal air gaps between the coolant inlet pipe and the casing and between the coolant outlet pipe and the casing for avoiding the entry of water into the casing.
Japanese Patent First Publication No. 2011-86761, assigned to the same assignee as that of this application, discloses the above type of power conversion apparatus equipped with a casing and grommets with protrusions on outer peripheries thereof. Specifically, each of the protrusions is in the shape of an annular ring extending on the entire circumference of a corresponding one of the grommets. Each of the grommets is disposed in one of cut-out portions of the casing with the protrusions pressed against an inner surface of the cut-out portion of the casing, thereby hermetically sealing between a corresponding one of the coolant inlet pipe and the coolant outlet pipe and the casing.
The installation of the grommets in the casing is achieved by putting the grommets in the cut-out portions of the casing from openings of the cut-out portions. If each of the grommets is viewed from the opening of the cut-out portion, it is impossible to visually perceive the whole of the protrusions of the grommet, in other words, it is difficult to check whether the protrusions of the grommet are correctly pressed in contact with the inner wall of the cut-out portion to establish a desired hermetic seal therebetween.